Butterfly kills from Bt corn debunked by researchers

So, how many millions of people saw the sensationalistic TV news stories a while back about how pollen from Bt corn was killing monarch butterflies?

There were certainly plenty of opportunities as TV anchors, dripping concern, told how pollen from the genetically engineered plants was drifting to the milkweed plants on which the butterfly caterpillars feed. All this accompanied, of course, by film of the gorgeous butterflies.

So, how many millions of people saw stories on TV and in the major newspapers that scientists have conclusively established that risk to the butterflies is “insignificant”? Not many, because those stories apparently didn't have the viewer/reader appeal of the ones about dead butterflies.

The whole thing was a tempest in a teapot from day one — a story based chiefly on the preliminary findings of a single very small study, without collaboration by other scientists to lend validity to the allegation. A number of reputable scientists subsequently debunked the “killer pollen” assertions, but their statements got nowhere the distribution of the original story.

It was announced just a few days ago that research conducted by a group of scientists coordinated by USDA's Agricultural Research Service found “no significant risk to monarch butterflies from environmental exposure to Bt corn pollen.”

The research was published in the Proceedings of the National Academy of Sciences, and the findings made available to the media, which mostly ignored the information.

Here's what the scientists found: For pollen from Bt corn to have a toxic effect on the Monarch caterpillars, the insects had to be exposed to levels in excess of 1,000 grains per centimeter. Corn pollen levels on milkweed during the two weeks of crop pollen shed averaged only 170 grains per centimeter within the corn fields.

Several field studies showed much lower levels, ranging from about 50 grains per centimeter at the edge of a corn field to less than 1 grain just a few feet away from the edge.

Only one variety of Bt corn was found to have a negative effect on the caterpillars at very low concentrations, but it was an old Bt variety, is not widely planted, and will likely be phased out entirely by 2003.

All the studies have undergone critical peer review by independent experts to insure the validity of the scientific methods, analysis, and conclusions.

The cooperation between researchers from many separate institutions was “extraordinary,” USDA said. In fact, “the way in which this research was done is being considered as a model for conducting risk assessment research.” The studies included exchanges of information between butterfly biologists, corn experts, pest specialists, and others, all working to insure that they scientifically valid.

Even publication of the data was handled in an unusual, coordinated fashion, with researchers themselves pooling their findings and submitting everything to a single scientific journal for peer review. By publishing exposure, toxicity, and risk analysis studies at one time in one journal, scientists and policymakers could more easily evaluate the information.